Function validate_non_nullable 

pub fn validate_non_nullable<C: Conventions>(input: TokenStream) -> TokenStream

#[derive(ValidateNonNullable)]: a validation function for a merge patch DTO, mirroring a domain merge patch model.

A field named differently on the domain merge patch model maps onto it with #[equivalent_field(name)]; validation errors keep the DTO’s field names. The mirrored struct is a merge patch model or another mirror (e.g. a gRPC message mirroring the DTO): every one implements queryweave::NullableFields under its own names, every chain ending at a merge patch model.

Attributes: validate_non_nullable, equivalent_field.